1. Field of the Invention
This invention concerns ignition systems in general, and more specifically relates to an improved ignition system for use with internal combustion engines. It is especially concerned with a controlled-spark-duration ignition system that employs a continuous-wave oscillator.
2. Description of the Prior Art
This invention deals particularly with ignition systems of a type like that set forth in the following three U.S. patents, i.e. U.S. Pat. No. 3,818,885 which discloses the same basic type of ignition system; and U.S. Pat. No. 3,792,261 which discloses a photo electric distributor of a type which may be used with this invention; and U.S. Pat. No. 3,861,369 which discloses an ignition system and particularly an electronic control circuit that is for use with this type of ignition system. Especially in connection with some types of internal combustion engines it has been found beneficial to provide for double ignition timing controls with a different basic time setting for each. These are provided so that under certain conditions a complete shift of the ignition timing base may be made in order to change from a given spark timing condition, e.g. top dead center, to a given angle of a retard or other substantial basic change in the ignition timing.
While the basic concept of providing such a dual ignition timing system is quite well known, all the known proposals for thus providing two systems which may be selectively employed, only have been disclosed with systems that use conventional "points" for the ignition timing controls. Consequently, they dealt with one shot types of ignition signal and such do not involve controlled duration sparks, but rather mere controlled initial timing of spark signals.
Furthermore, with the prior systems, when spark timing control is shifted from one of the two sets of "points" to the other at the instant when a spark is called for, a spark could be missed.
Consequently, it is an object of this invention to provide for an ignition system related to a controlled duration continuous-wave spark signal, which has dual spark timing elements on the distributor so that the ignition timing may be shifted from one basic timing control to another under desired conditions.